Science Olympiad Captains’ Tryouts 2018 Rocks & Minerals duPont Manual High School Name: Date: Score: ________ / 78 Part I: (25) points Based on the image and information provided, fill in the table. Each answer is worth (1) point.

You can scratch this sample with a penny, but not your fingernail.

Name:

Celestite

Chemical Formula:

SrSO4

Hardness (Mohs):

3-3.5

Streak:

White

Crystal System (class unnecessary):

Orthorhombic

You can scratch this sample with a steel nail.

Name:

Sphalerite

Chemical Formula:

ZnS

Hardness:

3.5-4

Streak:

White, but accept light brown

Crystal System:

Isometric

You notice this sample floats in a beaker of liquid with specific gravity 2.1.

Name:

Gypsum (Satin Spar), give ½ point if specification is not made

Chemical Formula:

CaSO4 X 2H2O

Hardness:

2

Streak:

White

Crystal System:

Monoclinic

You notice the earthy luster of this sample.

Name:

Limonite

Chemical Formula:

FeO(OH) X nH2O

Hardness:

4-5.5

Streak:

Yellow to brown

Crystal System:

Amorphous

You can’t scratch this sample with a copper penny.

Name:

Tremolite

Chemical Formula:

Ca2(Mg, Fe)5Si8O22(OH)2

Tenacity:

Brittle

Streak:

White

Crystal System:

Monoclinic

Part II: (9) points Using the terms provided on the right, fill in the chart. Each answer is worth (1) point.

Andesite Basalt Diorite Felsic Gabbro Granite Intermediate Mafic Rhyolite

1 Felsic

2 Intermediate

3 Mafic

4 Rhyolite

5 Andesite

6 Basalt

7 Granite

8 Diorite

9 Gabbro

Part III: (10) points Based on the image, describe the specimen’s geological setting of formation and process of formation. Each answer is worth (2) points.

(1) point for setting, (1) point for process. Formed from laterite soil severely leached of silica and other solubles in a wet tropical or subtropical climate.

Found largely in oxidized portions of copper deposits; formed by action of carbonated water on copper-containing minerals. OR from copper-containing solutions reacting with limestone.

Formed from when deposits in places such as dry lakes and saline lake shorelines, salt beds, and salt domes evaporate.

Formed by fluorine-bearing vapors given off during last stages of crystallization of igneous rocks in igneous environments.

Formed as secondary altering material, usually from weathering, in igneous, metamorphic, and sedimentary environments. Most often found near oxidized surface where it has altered.

Part IV: (21) points Based on the image provided, fill in the table. Each answer is worth (1) point, with the exception of those marked otherwise. Note: When answering for classification, be specific. If sedimentary, is the specimen clastic, chemical, or organic? If igneous, is the specimen plutonic or volcanic? No partial points will be given.

Name: Breccia

Most common economic use:

Ornamental

Classification:

Sedimentary (clastic)

Define the “impact” variety of this specimen:

Deposit of angular rock debris produced by impact of asteroid or other cosmic body

Name: Rhyolite

Classification:

Igneous (volcanic)

Basic minerals of composition (at least 3):

Quartz, alkali feldspar, biotite, hornblende (any 3)

Most common texture:

Aphanitic to partly glassy, also accept aphanitic-porphyric

Name: Chert

Classification:

Sedimentary (chemical)

Formation (2 pts):

Precipitation of silica from seawater OR skeletons of algae and protozoans accumulate and crystallize OR partial replacement of limestone with silica OR silica replacement of wood from groundwater action

Economic use:

Flint

Name: Gabbro

Texture:

Phaneritic

Minerals of composition:

Plagioclase feldspar, hornblende, augite, olivine (any 3)

What is the diabase variety of this rock used for?

Crushed stone for concrete aggregate, road metal, ballast, granules

Name: Gneiss

Degree of metamorphosis:

High

Minerals of composition:

Orthoclase, quartz, biotite, hornblende (any 3)

Sedimentary parent rock (at least 2):

Shale, sandstone, conglomerates (include breccia) (any 2)

Part V: (7) points Using your knowledge of Bowen’s Reaction Series, answer the following short answer questions. Points vary between questions. Note: Some of the answers will include minerals not on the 2017 Rocks & Minerals list.

1. A magma is at a very high temperature and pressure. a. If a rock forms from this magma, what minerals would compose it if it were intruded into

the Earth? (1) point Olivine, pyroxene, calcium plagioclase

b. What minerals would it have if it were extruded onto the surface of the earth? (1) point

Olivine, pyroxene, calcium plagioclase

c. What would be the difference in texture between these rocks? (1) point The first is phaneritic, the second aphanitic because of the cooling rates.

2. A basalt specimen has quartz in it. Where did the quartz come from? (1) point

From the rock surrounding the magma chamber

3. The only mineral in a rock is olivine. How could this happen? (3) points There were no chemicals to form the feldspars, and the rock cooled to slowly for the discontinuous reactions to take place, OR there was not enough silica for the reactions to take place

Part VI: (6) points Identify the crystal structures depicted. 1 Cubic 2 Tetragonal 3 Hexagonal 4 Orthorhombic 5 Monoclinic 6 Triclinic Part VII: Tiebreaker Identify the five conditions that a mineral, by definition, must fulfill. Each condition is worth (1) point. Must be naturally occurring, of inorganic compounds, a solid element or compound, have a regular internal crystal structure, and have a definite chemical composition